1. Field of the Disclosure
The present disclosure relates to a brushless motor.
2. Discussion of the Related Art
Generally, almost every vehicle employs an electric power-assist steering system. Such an electric power-assist steering system generates an assist force based on the steering torque and the steering angle in order to enhance the steering performance of the vehicle.
That is, a steering system that assists a steering force of a vehicle with a separate power is used to enhance the motion stability of a vehicle.
Conventionally, the auxiliary steering device uses hydraulic pressure, but an Electronic Power Steering (EPS) system adapted to transmit a rotation output of an electric motor to a steering shaft via a speed reduction mechanism has been increasingly employed these days from a viewpoint of a reduction in engine load, a reduction in weight, an enhanced steering stability and a quick restoring force.
The EPS system is configured such that an Electronic Control Unit (ECU) drives a motor in response to steering conditions detected by a speed sensor, a torque angle sensor and a torque sensor to enhance a steering stability and provide a quick restoring force, whereby a driver can safely steer a vehicle.
The EPS system is also such that a motor assists a torque manipulating a steering wheel to allow a driver to steer a vehicle with less power, where the motor employs a Brushless Direct Current (BLDC) motor.
The BLDC motors have been increasingly used because the brushless motors are excellent in maintenance property, have a small size, and are capable of generating a high torque.
The BLDC motor generally forms an exterior look by coupling of a housing with a cover member, an inner circumferential surface of the housing is provided with a stator, and the stator is centrally formed with a rotor rotatably mounted in electrical interaction with the stator. The rotor is rotatably supported by a rotation shaft, and an upper surface of the rotation shaft is connected by a steering shaft of a vehicle to provide a power assisting the steering of the vehicle as mentioned above. The stator of EPS motor thus configured serves to supply an electric power to a wound coil via busbar.
The stator includes a core and a coil wound on the core, and in general, a motor used for a vehicle is employed with a plurality of coils connected in parallel for loss reduction. Thus, the coil is extended to an input/output terminal, and integrated and connected at the terminal during parallel connection. In order to integrate and connect the coil arranged in parallel, a busbar is coupled to an upper surface of the stator, and in order to couple the busbar, a coil terminal of coils respectively wound on the upper surface of stator, and the busbar is connected to the coil terminal.
The busbar is fixedly arranged with a plurality of metal members electrically connected to the coil terminal which is then insulated by an insulator. The busbar takes an approximate shape of a doughnut to correspond to a shape of the stator. The busbar is arranged at a periphery with terminals for connecting the coil terminal.
The shape of a busbar is change in response to a connected electrical power, and in general, the EPS motor is configured such that respective input/output terminals are sequentially arranged to a periphery of the busbar through a 3-phase circuit.
However, there is a disadvantage in forming the busbar terminal bent to the busbar in that each busbar terminal must be bent at a predetermined size, and it is too much complicated to insert and fuse the coil into the busbar terminal, frequently generating faulty works.
Particularly, molds are complicated, and materials are wasted because of complicated shape of a fusing unit and generation of too much of scraps when the busbar terminal is manufactured using a press forming method, in a case the busbar terminal and the coil are fixed by being fused, and fusing unit is formed in a U-shape.
Another disadvantage is that a large quantity of straight portions of a coil for pulling the coil is required to resultantly waste a large quantity of coils, because the U-shaped ring type busbar terminal must be penetrated through a U-shaped ring, pulled, fused and cut.